The response to arterial injury in vivo is mediated by a complex set of cellular interactions involving endothelial and smooth muscle cells. Following damage to the arterial wall, growth factors and cytokines are released locally and induce cellular proliferation through autocrine and paracrine mechanisms. A common and clinically significant setting for such injury is balloon angioplasty wherein blood vessels narrowed by atherosclerotic deposits are opened using an inflatable balloon. Dilation of the occluded vessel can result in a reactive cellular proliferative response which leads to renarrowing (restenosis) of the arterial lumen. Blood flow is compromised by hyperplasia of the intimal (adjacent to the lumen) layer of the artery and to deposition of extracellular matrix components. Restenosis occurs in approximately 30% of coronary artery angioplasties, thereby presenting a major roadblock to the successful treatment of cardiovascular disease.
A number of approaches for controlling smooth muscle cell proliferation following angioplasty have been attempted, including angiotensin converting enzyme (ACE) inhibitors and antisense RNA directed against cell cycle control proteins (Rakugi et al., (1994) J. Clin. Invest., 93:339–346; Simons et al., (1992) Nature, 359:67–70). Although these pharmacological approaches have been somewhat effective in preventing the neointimal hyperplasia associated with balloon angioplasty in a rat carotid model, the application of these approaches to human disease has been unsuccessful.
Replication-deficient adenoviral vectors have been used in a number of promising approaches to gene therapy. Lemarchand et al. demonstrated transfer of the β-galactosidase and α1-antitrypsin genes into the endothelium of normal arteries and veins in sheep using an adenoviral vector (Circulation Res., 5:1132–1138, 1993; Proc. Natl. Acad. Sci. USA, 89:6482–6486, 1992). Lee et al. (Circulation Res., 73:797–807, 1993) demonstrated adenoviral vector-mediated transfer of the β-galactosidase gene into balloon-injured rat carotid arteries. These vectors have also been used to transduce mouse hepatocytes in vivo (Stratford-Perricaudet et al., (1990), Hum. Gene Ther., 1:241–256). In addition, expression of a recombinant β-galactosidase gene has been observed after infusion of an adenoviral vector into rabbit coronary arteries (Barr et al., (1994) Gene Therapy, 1:51–58).
Culver et al. (Science, 256:1550–1552, 1992) injected murine fibroblasts expressing the herpes simplex virus thymidine kinase (HSV-tk) gene into rats with a cerebral glioma. The rats were then given the nucleoside analog ganciclovir (GCV). Once GCV entered the cells expressing the HSV-tk gene, it was phosphorylated by the newly expressed thymidine kinase. Cellular kinases can also phosphorylate GCV, which is incorporated into replicating DNA (Smith et al., (1982) Antimicrob. Agents Chemother., 22:55–61) and causes premature chain termination. As this process inhibited DNA replication, only the actively dividing cells were killed. In this experiment the gliomas regressed completely both microscopically and macroscopically. Other nucleoside analogs capable of being modified by thymidine kinase, such as acyclovir (Elion et al., (1977) Proc. Natl. Acad. Sci. U.S.A., 74:5716–5720), have been used as targets for suicide inhibition of cellular replication.
Moolten et al. (Hum. Gene Ther., 1:125–134, 1990) induced lymphomas with Abelson leukemia virus in transgenic mice carrying the HSV-tk gene. Following treatment of 12 mice with GCV, 11 exhibited complete tumor regression.
Plautz et al. demonstrated in vivo regression of a transplantable murine adenocarcinoma transfected with a HSV-tk gene and treated with GCV. In these same experiments, expression of a HSV-tk-β-galactosidase construct in nondividing rabbit arterial cells was unaffected by GCV treatment, demonstrating the selectivity of this approach in the maintenance of quiescent cells and the elimination of rapidly dividing cells in vivo (Plautz et al., (1990) New Biologist, 3:709–715).
The efficacy of introducing a suicide gene into smooth muscle cells has not been previously addressed. For this reason, there exists a need for safe, effective methods of inhibiting neointimal hyperplasia after mechanical vessel injury. The present invention provides a solution to this need.